UBS, the embattled Swiss bank that has been Europe’s main casualty of the credit crunch, is facing a fresh assault after a former chief executive launched an activist campaign to break it up and overhaul its board.
Luqman Arnold, who was forced out of UBS in 2001 and led a failed bid for Northern Rock, the mortgage lender, revealed he had built up a 0.7 per cent stake in the bank, valued at $450m (£226m), through Olivant, his investment company based in London.





